So, this is a weird one to "spoil," being that there's not much of a cohesive story. But that's the point. By now, you've no doubt heard that Harley breaks the fourth wall in this issue, and goes further by making it her bitch. Harley wants her own comic book, and page after page, she speaks directly to Amanda Conner and Jimmy Palmiotti on who wold be good to draw it and discussing the positives and negatives of each artist... and then some.
This is one of those books where you have to read to get. Me describing each joke does it no justice. Some of my favorites are Harley complaining that Jim Lee just reused a page from hush, or Adam Hughes being "late," or maybe Harley deciding to go easy on being Jimmy up at his and Amanda's wedding, because sales on Batwing and All-Star Western aren't all too hot.
All in all, it's a super fun book, and the only thing that is really "spoilable" is that on the last page, an anonymous former patient of Harley's gives her the rights to some property on Coney Island.